C#: Object to string array. [*] to [] error (Knowing both VB.NET as well as C# helps)

[Charp]

Hi, I have been assigned to Convert a VB.NET project to C# and I got stuck. I am using a class called RsiOPCAuto, but I don't think that I'll have to go into to much detail into explaining how it works. Let's just get on with my issue.

So basicly what i do is grabbing an object from my class using this code:

public partial class FrmPartialMain : Form
{
RsiOPCAuto.OPCServer oOpcServer;
public FrmPartialMain()
{
InitializeComponent();
object RsiOPCAuto;
object oOPCList;
 
oOpcServer = new RsiOPCAuto.OPCServer();
oOPCList = oOpcServer.GetOPCServers();
 

So far, so good. By adding a watch I can see that oOPCList now have the value {string[1..4]}.

Now I want to put these four strings into a combo box. I do this with a simple for loop:

for (int i = 0; i <= oOPCList.Length; i++)
{
cboServer.Items.Add(oOPCList[i]);
}
 

Event though this object now functions as a string array both the oOPCList.Length and (oOPCList[i]) get errors:

.Length
Error 1 'object' does not contain a definition for 'Length' and no extension method 'Length' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?)
oOPCList[i]
Error 2 Cannot apply indexing with [] to an expression of type 'object'

I bet it's just the simplest thing but I just can't see it, help is very much appreciated and if there's anything else you need to know be sure to ask :-)

PS. It might be worth mentioning that I have tried some different ways to convert the object to a string array but I continuously get an error telling me that I can not convert system.string[*] to system.string[], which I guess is pretty obvious if it means what I think it means.

This is the VB.NET code that I am converting:

Friend Class frmPartialMain
Inherits System.Windows.Forms.Form
Dim oOpcServer As RsiOPCAuto.OPCServer
 Private Sub frmPartialMain_Load(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Load
        Dim RsiOPCAuto As Object
        Dim oOPCList() As Object
        Dim i As Integer
 
        oOpcServer = New RsiOPCAuto.OPCServer
        oOPCList = oOpcServer.GetOPCServers
        For i = LBound(oOPCList) To UBound(oOPCList)
            cboServer.Items.Add(oOPCList(i))
        Next i
 

[Plater]

You declared oOPCList as an object. You should declare it as a string[] (if that is really the type)

string[] oOPCList;

Or you can typecast it at point of usage, but I recomend declaring it to be string[] from the start

[Charp]

I tried that and it did not work, instead i had to use the following code:
IEnumerable<string> oOPCList;

oOPCList = ((Array)(object)oOpcServer.GetOPCServers()).Cast<s tring>();

I also had to change the for loop to a foreach loop:
foreach (var item in oOPCList)
cboServer.Items.Add(item);

The strange cast first to object, then to Array, and then to IEnumerable<string> via Cast<string> is needed because of the following:

GetOPCServers returns a dynamic type. Trying to access that dynamic instance in any way - even via a call to GetType triggers an InvalidCastException. Therefore, it first needs to be cast to object so it no longer is a dynamic type. After that, we can cast it to an Array, the only supported way in C# to work with non-zero-based arrays. But Array is not strong typed, so we append the call to Cast<string> to get a strong typed enumerable.

[Plater]

What does this give you?
string TypeName=oOpcServer.GetOPCServers().GetType().Name ;

That should tell you the actual type being returned(actually it tells you the type then I am using the Name property because it is a quick identifier)

[RhysW]

Additionally it also didnt have the parameter of length, usually the problem if something doesnt have length it will have count (a 1 based index not a 0 based index) just leaving this explanation here incase someone gets directed here from searching a problem with the same exception.

[Charp]

Yeah, Plater, I know. That line gives me the [][*] error again though.

[Plater]

Interesting. I have never seen anything fail on .GetType(), it should be a function on every single thing.

[Charp]

I was using RsiOPCAuto.dll library if you are curious an want to mess around with it yourself. I'm sure you can find it somewhere on the net.